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Microchip capillary electrophoresis: Improvements using detection geometry, on-line preconcentration and surface modification.

机译：微芯片毛细管电泳：使用检测几何形状，在线预浓缩和表面修饰进行改进。

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摘要

Capillary electrophoresis and related microfluidic technologies have been utilized with great success for a variety of bioanalytical applications. Microchip capillary electrophoresis (MCE) has the advantages of decreased analysis time, integrated sample processing, high portability, high throughput, minimal reagent consumption, and low analysis cost. This thesis will focus on the optimization of our previous microchip capillary electrophoresis coupled electrochemical detection (MCE-ECD) design for improved separation and detection performance using detection geometry, on-line preconcentration and surface modification. The first effort to improve detection sensitivity and limits of detection (LODs) of our previous MCE-ECD system is established by an implementation of a capillary expansion (bubble cell) at the detection zone. Bubble cell widths were varied from 1x to 10x the separation channel width (50 microm) to investigate the effects of electrode surface area on detection sensitivity, LOD, and separation efficiency. Improved detection sensitivity and decreased LODs were obtained with increased bubble cell width, and LODs of dopamine and catechol detected in a 5x bubble cell were 25 nM and 50 nM respectively. In addition, fluorescent imaging results demonstrate ~8% to ~12% loss in separation efficiency in 4x and 5x bubble cell, respectively. Another effort for enhancing detection sensitivity and reducing LODs involves using field amplified sample injection and field amplified sample stacking. Stacking effects were shown for both methods using DC amperometric and pulsed amperometric detections. Decreased LODs of dopamine were achieved using both on-line sample preconcentration methods.;The use of mixed surfactants to affect electroosmotic flow (EOF) and alter separation selectivity for electrophoretic separations in poly(dimethylsiloxane) (PDMS) is also presented in this thesis. First the effect of surfactant concentration on EOF was studied using the current monitoring method for a single anionic surfactant (sodium dodecyl sulfate, SDS), a single zwitterionic surfactant (N-tetradecylammonium-N,N-dimethyl-3-ammonio-1-propane sulfonate, TDAPS), and a mixed ionic/zwitterionic surfactant system (SDS/TDAPS). SDS increases the EOF as reported previously while TDAPS shows an initial increase in EOF followed by a reduction in EOF at higher concentrations. The addition of TDAPS to a solution containing SDS makes the EOF decrease in a concentration dependent manner. The mixed SDS/TDAPS surfactant system allows tuning of the EOF across a range of pH and concentration conditions. After establishing EOF behavior, the adsorption/desorption rates were measured and show a slower adsorption/desorption rate for TDAPS than SDS. Next, capacitively coupled contactless conductivity detection (C4D) is introduced for EOF measurements on PDMS microchips as an alternative to the current monitoring method to improve measurement reproducibility. EOF measurements as a function of the surfactant concentration were performed simultaneously using both methods for three nonionic surfactants, (polyoxyethylene (20) sorbitan monolaurate (Tween 20), polyoxyethylene octyl phenyl ether (Triton X-100), polyethylene glycol, (PEG 400)), mixed ionic/nonionic surfactant systems (SDS/Tween 20, SDS/Triton X-100, and SDS/PEG 400) and mixed zwitterionic/nonionic surfactant systems (TDAPS/Tween 20, TDAPS/Triton X-100, and TDAPS/PEG 400). EOF for the nonionic surfactants decreases with increasing surfactant concentration. The addition of SDS or TDAPS to a nonionic surfactant increases EOF relative to the pure nonionic surfactant. Next, separation and electrochemical detection of two groups of model analytes were explored using mixed surfactant systems. Similar analyte resolution with greater peak heights was achieved with mixed surfactant systems relative to the single surfactant system. Finally, the utility of mixed surfactant systems to achieve improved separation chemistry of biologically relevant compounds in complex sample matrixes was demonstrated in two applications, which include the detection of catecholamine release from rat pheochromocytoma (PC12) cells by stimulation with 80 mM K+ and the detection of reduced glutathione (GSH) in red blood cells (RBCs) exposed to fly ash suspension as a model environmental oxidant.
机译：毛细管电泳和相关的微流体技术已成功用于各种生物分析应用。微芯片毛细管电泳（MCE）具有减少分析时间，集成样品处理，高便携性，高通量，最小的试剂消耗和低分析成本的优点。本文将着重于优化我们以前的微芯片毛细管电泳耦合电化学检测（MCE-ECD）设计，以利用检测几何结构，在线预浓缩和表面修饰提高分离和检测性能。我们在以前的MCE-ECD系统中提高检测灵敏度和检测限（LOD）的第一项努力是通过在检测区域实施毛细管膨胀（气泡池）而建立的。气泡池的宽度在分离通道宽度（50微米）的1倍至10倍之间变化，以研究电极表面积对检测灵敏度，LOD和分离效率的影响。随着气泡池宽度的增加，检测灵敏度得到提高，LOD降低，在5x气泡池中检测到的多巴胺和邻苯二酚的LOD分别为25 nM和50 nM。此外，荧光成像结果表明在4x和5x气泡池中分离效率分别损失8％至〜12％。增强检测灵敏度和降低LOD的另一项工作涉及使用现场放大的样品进样和现场放大的样品堆叠。两种方法都显示了使用直流安培和脉冲安培检测的叠加效果。两种在线样品预富集方法均可降低多巴胺的LODs。本文还提出了使用混合表面活性剂影响电渗流（EOF）和改变分离选择性以进行聚二甲基硅氧烷（PDMS）电泳分离的方法。首先，使用电流监测方法研究了单一阴离子表面活性剂（十二烷基硫酸钠，SDS），单一两性离子表面活性剂（N-十四烷基铵-N，N-二甲基-3-铵-1-丙烷）的表面活性剂浓度对EOF的影响。磺酸盐（TDAPS）和混合的离子/两性离子表面活性剂系统（SDS / TDAPS）。如先前报道，SDS增加EOF，而TDAPS显示EOF最初增加，然后在较高浓度下EOF降低。向含有SDS的溶液中添加TDAPS会使EOF以浓度依赖的方式降低。 SDS / TDAPS混合表面活性剂系统可在一系列pH和浓度条件下调节EOF。建立EOF行为后，测量吸附/解吸速率，结果表明TDAPS的吸附/解吸速率比SDS慢。接下来，引入电容耦合非接触式电导率检测（C4D）进行PDMS微芯片上的EOF测量，作为电流监测方法的替代方法，以提高测量的可重复性。对于两种非离子表面活性剂，同时使用两种方法同时进行EOF测量，作为表面活性剂浓度的函数（聚氧乙烯（20）脱水山梨糖醇单月桂酸酯（Tween 20），聚氧乙烯辛基苯基醚（Triton X-100），聚乙二醇（PEG 400） ），混合的离子/非离子表面活性剂系统（SDS / Tween 20，SDS / Triton X-100和SDS / PEG 400）和混合的两性离子/非离子表面活性剂系统（TDAPS / Tween 20，TDAPS / Triton X-100和TDAPS / PEG 400）。非离子表面活性剂的EOF随着表面活性剂浓度的增加而降低。相对于纯非离子表面活性剂，向非离子表面活性剂中添加SDS或TDAPS会增加EOF。接下来，使用混合表面活性剂系统探索了两组模型分析物的分离和电化学检测。相对于单一表面活性剂系统，混合表面活性剂系统可实现相似的分析物分辨率和更高的峰高。最后，在两种应用中证明了混合表面活性剂系统可用于改善复杂样品基质中生物相关化合物的分离化学的效用，包括通过80 mM K +刺激检测大鼠嗜铬细胞瘤（PC12）细胞中的儿茶酚胺释放以及检测暴露于粉煤灰悬浮液中的红细胞（RBC）中还原型谷胱甘肽（GSH）的含量作为模型环境氧化剂

著录项

  • 作者

    Guan, Qian.;

  • 作者单位

    Colorado State University.;

  • 授予单位 Colorado State University.;
  • 学科 Chemistry General.;Chemistry Analytical.
  • 学位 Ph.D.
  • 年度 2012
  • 页码 147 p.
  • 总页数 147
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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